An OTN has a high-capacity long-distance transport capability, may provide multiple protection manners and end-to-end monitoring management and may provide a high-reliability support platform for data transmission, and moreover, the OTN provides a circuit-based interaction technology to fully ensure a guaranteed bandwidth, and is an inevitable choice for an underlying transmission technology.
An OTN is a transport network which is organized in an optical layer on the basis of a wavelength division multiplexing technology, and is a backbone transport network of the next generation. A frame structure of the OTN may support mapping and transparent transmission of various client signals, such as a Synchronous Digital Hierarchy (SDH), an Asynchronous Transfer Mode (ATM) and the Ethernet. Along with explosive growth of Internet Protocol (IP) services and other packet-transport-based data services transported on a network, the OTN may take data services as bearing main bodies in the future. A transmission delay index is a key index for transmission of a data service, and thus, how to rapidly and effectively know an end-to-end delay through a path of a transmission network is very important.
At present, there are mainly three technologies for implementing measurement of an end-to-end delay of an OTN device: (1) a length of an optical fibre is divided by a propagation speed of light in the optical fibre, in which since the propagation speed of the light is very high, the OTN device has a transit delay and the length of the optical fibre is not so easy to be determined accurately, the method may only provide a basis for rough estimation; (2) a delay testing function provided by a testing instrument of a third party is adopted for assisting in testing, such a method is usually used for start and acceptance testing of OTN device, its result is widely accepted by the industry, but such a method has such a requirement that the instrument is connected to the device and the device has an idle port, and may not be applicable to some existing network environments; and (3) a new delay measurement characteristic is added to standard G.709/Y.1331, such a method redefines overhead bytes reserved in Optical Channel Data Unit k (ODUk) and Tandem Connection Monitor i (TCMi) before and may measure a delay of end-to-end ODUk or any TCMi, and although such a method is simple, existing network device may be greatly modified, and such a standard is inapplicable to the condition of existence of relay device.